Which of the following is a non-invasive method for assessing fetal heart rate?

Auscultation with a Doppler device is a non-invasive method for assessing fetal heart rate. This technique involves using a handheld Doppler ultrasound device that emits sound waves to detect the heartbeat of the fetus. As the sound waves bounce off the fetal heart, they produce audible sounds that can be heard through the device. This method allows for real-time monitoring of the fetal heart rate without the need to insert any instruments into the mother's body, making it completely non-invasive.

In contrast, other methods such as the fetal scalp electrode involve invasive procedures, as they require placement of an electrode directly onto the fetal scalp through the cervix. The external tocodynamometer, while non-invasive in the sense that it doesn't involve internal instrumentation, primarily measures uterine contractions rather than directly measuring fetal heart rate, making it less relevant in this context. The intrauterine pressure catheter, similarly, is an invasive tool used to measure intrauterine pressure and does not assess fetal heart rate directly. Therefore, auscultation with a Doppler device stands out as the primary non-invasive approach for evaluating fetal heart activity.